Drive tests are run in a radio network, usually by the employees of an operator or by a third party, for many reasons, such as determining radio coverage. Such test runs are expensive (both in terms of network resource costs and monetary costs due to the man-hours involved) and time consuming.
Due to these drawbacks, a new MDT feature was introduced in the standards to automatically request and collect, from a User Equipment (UE), different measurements and event information. For example, in 3rd Generation Partnership Project (3GPP) Technical Specification (TS) 37.320 V.12.2.0, MDT measurement configurations and reporting schemes are defined. The standard 3GPP TS 37.320 applies to a UE in a Universal Mobile Telecommunications System (UMTS) or in a Long Term Evolution (LTE) system.
In the following, several problems not hitherto realized by the prior art will be discussed.
Basically, there are two types of MDT procedures as defined in 3GPP 37.320: (1) ‘Logged MDT procedures’ used for a UE in RRC_IDLE state (wherein ‘RRC’ stands for Radio Resource Control and is defined in 3GPP TS 36331 V.12.3.0) and recently also used for UE in RRC_CONNECTED state; and (2) ‘Immediate MDT procedures’ used for a UE in RRC_CONNECTED state. The MDT measurement (re)configuration and control (such as instructions ‘start’/‘stop’) can be received only by a UE in the RRC_CONNECTED state. This means that there is no possibility to control MDT procedures for UEs which have entered the RRC_IDLE state until they are back into RRC_CONNECTED state, even though the logging of MDT measurements may be very resource demanding (e.g., in terms of UE battery, memory, time, processing, etc.) and the logs may be very large.
As a non-liming example, a UE may enter the RRC_CONNECTED state at time t1, may receive an MDT configuration and then transit to RRC_IDLE state at time t2. At time t3>t2 (i.e., time t3 is later in time than time t2), the operator may want to stop MDT configuration for some reason (e.g., to save UE resources in an emergency situation or to better control measurement collection from one or multiple UEs in certain network situations). With the current standard, the UE has to be in RRC_CONNECTED to be able to receive an instruction to stop a running MDT log procedure. However, depending on the subscriber behavior, the UE may transit to connected mode (e.g., RRC_CONNECTED) again at t4, which may be much later in time than t3. As a result, from t3 until t4, the UE may be running an unwanted MDT log, which in turn unnecessarily consumes UE resources.
In a related scenario, the MDT trace report can be triggered for one particular MDT log trace id. However, in case of presence of multiple MDT logs, there is no possibility to report multiple MDT log results into one single report.
Moreover, although for the UE in RRC_CONNECTED state the network may dynamically control (e.g., ‘start’/‘stop’) MDT traces, it has been found that there exists no flexible solution for stopping MDT traces. In addition, there is no solution to either resume a stopped MDT trace or to aggregate an MDT log for a UE in the connected mode (such as RRC_CONNECTED).